The attention of the nuclear industry has been internally focused on the inherent dangers of producing power from fissionable products. Although no actual damage to the environment or detrimental effects on personnel have been documented over the many years of nuclear power production, the slightest rumor of mulfunctions of specific nuclear power installations have inflamed the public and caused the over-reaction of governmental regulatory authorities. The industry is expending huge efforts to placate the public and regulatory agencies by reexamining and modifying all its safety precautions subject to criticism.
From the birth of nuclear power generation, the quantity of noble gas emissions from a nuclear process has been of constant concern to the industry. The detectors brought into direct contact with noble gases are fully developed. These detectors are typically of the scintillation type and their count levels have been utilized to indicate and/or control.
The environmentalists have demanded the detectors respond to "As Low As Resaonably Achievable" (ALARA) levels. More specifically, the demand in the past has been for a detector which will include in its range 1.times.10.sup.-7 .mu.Ci/cc of noble gases. Presently, the industry is being required to provide the detector with a sample system which will be dependably operative when emissions of noble gases are in the post-accident phase. Therefore, a sample system is demanded which will supply the detector system with a representative sample, both when noble gas emission is very low and yet be able to shift to a mode of operation which allows the detector system to function when the quantity of noble gases surges above the so-called non-accident range during post-accident periods.
It is readily evident that the system must provide a representative sample in both modes of operation. The first mode presents an effluent sample to the sample chamber which is simply drawn off from the normal circuit. The problem descends when noble gases of this sample quantitatively exceed the range of the detector system responsive to the sample in the chamber. The problem is that of quickly replacing the sample in the chamber with one which is in a second mode of reduced concentration in order for the range of variation to be compatible with the detector system.